The present invention relates to an electrode design for the application of neurological stimulus to a patient in the form of current pulses from a pulse generator, and most particularly to a novel dual-terminal electrode designed particularly for the controlled stimulation of underlying nerve tissue to produce involuntary muscle contractions or responses that can be employed as a monitoring tool by anesthesiologists.
In recent years, anesthesiologists have become concerned with the monitoring and control of the effects of nondepolarizing neuromusclar blocking agents on patients both during and after surgical procedures. As is well known, anesthetization procedures are performed using a number of anesthetizing agents, the type and flow rate of the respective agents being controlled by the anesthesiologist during the surgical procedures. In this regard, the anesthesiologist will utilize some form of muscle relaxant and these are often nondepolarizing, requiring the administration of a reversing agent after the surgical procedure to reverse the muscle blocking effects thereof.
One method which has been employed to monitor the effects of these nondepolarizing agents, is to electrically stimulate the patient's nerve tissue to produce involuntary muscle contraction. Since the strength and frequency of the pulse applied is known and can be controlled, a comparison between the patient's reactions prior to administration of the anesthetic and at intervals during and after anesthetization provide an indication as to the muscle blocking effect of the relexant. Accordingly, the anesthesiologist monitoring of the involuntary muscle contraction provides an aid to the anesthesiologist in determining the dosage of the relaxant to be applied to the patient. Further, with regard to non-polarizing reactions, the degree of involuntary contraction observed after the surgical procedure, also provides a useful aid in determining the dosage of the reversing agent to be administered to the patient. A more detailed discussion of this general procedure can be found in U.S. Pat. Nos. 3,364,929 and 3,565,080.
The electrode design of the present invention provides a convenient and reliable construction that enables the proper application of nerve stimulating pulses, thereby aiding in the overall monitoring process. In this regard, the electrical terminals required in the transcutaneous application of current to the nerve tissue are provided in a single electrode structure, and are isolated electrically, so as to insure that the current passes through the patient's body tissue. The electrode is also disposable and preferably pre-gelled with the desired quantity of electrolytic gel being provided in the reservoir chambers. More specifically, the diameter and depth of the reservoir chamber, and the spacing between the respective chambers provided by the barrier segment of the base section are parameters which are determined in relation to the quantity of gel to be employed, and are selected such that upon mounting of the electrode to the skin of a patient, the electrical isolation of the respective chambers will be maintained and the gel from the respective chambers will not be co-mingled. Accordingly, upon the application of voltage across the respective terminals, a current pulse will flow from the terminal means and associated gel of a first one of said reservoir chambers to and through the body tissue of the patient to the gel and terminal means of the other of said reservoir chambers. It can be appreciated, that if the respective chambers were not electrically isolated, or if the gel quantities co-mingled, current could pass along the outer skin surface and the desired transcutaneous application of pulses to the nerve tissue would not occur, or would be adversely affected.
From the above discussion, and the detailed discussion of the illustrated embodiment to follow, it is believed that the advantages and features of the invention will become apparent. In this regard, the detailed description to follow will be had in conjunction with the accompanying drawings, wherein like reference numerals are used throughout to designate similar elements and components.